The invention relates to a process for effecting a chemical conversion by contacting a substrate in the liquid phase with an immobilized enzyme.
It is known to chemically convert an organic or inorganic compound into one or more other compounds by putting a solution of the substrate into contact with an immobilized enzyme or mixture of enzymes. Chemical conversion here comprises any change of the molecular structure of an organic or inorganic compound, such as those caused by hydrolysis, oxidation, reduction, isomerization, or racemization. Enzymes can be immobilized by physical or chemical binding to an organic or inorganic material or by crosslinking the enzyme or cell material with enzymatic activity, optionally in the presence of a filler.
On a technical scale, glucose is thus converted into a mixture of glucose and fructose by means of immobilized glucose isomerase, and N-acetyl L-amino acids are deacylated by means of immobilized amino acylase. In this process it is customary to pass the solution of the substrate through a fixed or fluidized bed of immobilized enzyme particles. Owing to the loss of enzymatic activity, the content of the reactor must be renewed at intervals. For reasons of process economy, it is customary in nearly all cases to replace the immobilized enzyme preparation as soon as its activity has dropped to a given value, usually 20 to 25% of the original activity, both in a discontinuous process in a single reactor and in a semicontinuous process in a single series-connected reactors. A drwaback of this process is that the residual activity of the enzyme preparations is not utilized.
The use of a fixed bed of enzyme particles has the additional drawback that the pressure build-up of such a bed is great owing to coagulation or swelling of the enzyme particles. It is also possible that channels are formed in the fixed enzyme bed. It is an object of the present invention to provide a process in which the enzymatic activity of the enzyme preparation can be utilized fully or almost fully. Another object is to make the conversion of the substrate as complete as possible.